1. Technical Field
The present invention relates to an optical integrated device and an optical integrated device manufacturing method.
2. Related Art
An optical integrated device is known in which a semiconductor laser, an optical waveguide, and a modulator are integrated monolithically on a single substrate, as shown in Patent Document 1, for example.
Patent Document 1: K. Shinoda, et al., “Highly reliable operation of InGaAlAs/InGaAsP integrated lasers,” Indium Phosphide & Related Materials, 2007. IPRM '07. IEEE 19th International Conference, IEEE, May 2007, pp. 39-42
In a monolithic integrated optical integrated device, there is a region where an optically active element that includes an electrode, such as a semiconductor laser, is coupled to another element. In the optical integrated device, the region where the optically active element and the other element are coupled is usually formed using a regrowth technique. However, when current flows from the electrode of the optically active element to the interface between the optically active element and the other element, generation and propagation of crystal defects is promoted. These crystal defects degrade the characteristics of the elements and decrease the reliability of the optical integrated device, particularly for the optically active elements. Therefore, a decrease in the current flowing through this interface is desired.
There is a proposal for offsetting the electrode of the optically active element from the interface between the optically active element and the other element, in a direction away from the other element, in order to restrict the current flowing through the interface between the optically active element and the other element. However, when the offset amount of the electrode is too small, the current flowing through the interface between the optically active element and the other elements cannot be decreased, and therefore the degradation of the element characteristics and the loss of reliability cannot be prevented. Furthermore, if the offset amount of the electrode is too large, the current flowing through a region near the interface between the optically active element and the other element becomes small. As a result, the optical absorption increases in this region, and the optically active element is degraded. Accordingly, when offsetting the electrode of the optically active element from the interface between the optically active element and the other element, in a direction away from the other element, it is necessary to control the position of the interface and the position of the electrode with accuracy in a range of several microns. However, due to restrictions on the accuracy of lithography, the yield for the optical integrated device manufacturing process and the characteristics of the optically active element are decreased. Therefore, another method is desired to decrease the current flowing through the interface between the optically active element and the other element.
The optically active element is an element that receives power from an electrode and uses this power. The optically active element may be a semiconductor light emitting diode element, a semiconductor laser element, an optical amplifier, or an EA modulator, for example. These optically active elements realize effects such as natural emission, induced emission, and electro-optical effects.